No living organism can survive without water. We tend to take for granted that, when we open the tap, we’ll have clean water to drink or bathe in. Or, when we go to the beach, we won’t be poisoned by dangerous chemicals. However, as natural forests and fields are replaced with buildings, roads, and parking lots, stormwater runoff increases. It’s this runoff, which seeps into the groundwater, that has the potential to pollute the water we depend on for drinking and recreation. Such construction alters the landscape and natural watershed. Without foresight and periodic adjustments, this will result in the pollution of groundwater, and ultimately our water sources.
Although hardly noticeable, groundwater is one of our most critical natural resources. When rain falls, it soaks into the ground, adding to the groundwater. This eventually seeps into an aquifer, from where we get our water supply. Keeping the groundwater free from pollutants, therefore, is important not just for our health, but for the health of virtually all living organisms, including fish and other wildlife and the general biodiversity of our planet.
While rainwater can generally be considered safe to drink if it falls through an unpolluted environment, major problems can begin once it flows through the ground, especially during storms. As the stormwater quickly flows, it can severely damage the bodies of water it passes through and empties into, leading to flooding, danger to flora, fauna, and humans, and loss of the natural habitat. Shore areas can become off-limits not just to human recreation, but also hostile to wildlife such as fish and crabs.
Stormwater runoff, precipitation that has not been absorbed by the ground, washes over the surface of the land picking up pollutants as it travels. It may collect animal waste, fertilizers, soil particles, petroleum products, litter, and other chemicals through the sewer system. These pollutants impair water quality by increasing levels of nitrogen, phosphorus, and other chemicals, allowing algae and other unhealthy microorganisms to thrive.
In developed areas, it doesn’t take much rain to produce this kind of runoff. Every square foot of surface area, such as parking lots, roads and rooftops generates .62 gallons of water that needs somewhere to go. During storms, when the flow is too much for the sewer system to handle, water gets backed up.
Stormwater management is not only good for the environment, developers are legally bound to provide for it. Commercial properties in particular need to ensure that their stormwater runoff is controlled. This is where Low Impact Development (LID) comes into play. Green infrastructure such as rain gardens and, for larger areas, retention ponds, provide for biological water filtration, utilizing aquatic plants that naturally feed on the nitrates leaving fewer nutrients to support algae growth. Retention ponds are often designed with additional drainage and filtration systems. Layers of materials like mulch, gravel, and soil are specially designed to filter out pollutants and unwanted materials before the stormwater can reach local waterways. Retention ponds are designed to change in reaction to the rainfall, being empty in drier periods. During heavy rainfall they gather water and release it slowly, preventing flooding and soil erosion.
Retention ponds are mainly used in commercial or agricultural settings for satisfying municipal permitting requirements. In many areas, the homeowners themselves are responsible for this type of environmental protection. Before you buy a home, it is best to check who will be responsible for dealing with this problem.
There are different types and sizes of retention ponds. Some may look like grassy wetlands in the rainy season. More elaborate types may feature rock boundaries, waterfalls, and lush surrounding vegetation. No matter what type of retention pond it is, they need cleaning out and maintenance every few years in order to remain efficient. If they are not maintained properly, not only will they be ineffective, but they can create health hazards and flooding due to poor drainage. Old ineffective retention ponds can have stagnant water, no aeration, no circulation, and high nutrient loads which feed the algae bloom choking off native plants and animals.
Steps needed to improve the condition of failing retention ponds include draining out the water, cleaning out sediment and problematic materials that have accumulated at the bottom. A liner is then installed at the bottom which is anchored down with a mix of river rock and soil. Covering up the liner lengthens the lifespan of the liner, protecting it from UV radiation. Sometimes a drainage system is needed underneath, draining out to a sump area.